The present invention relates to a paper shear for a serial printer and particularly to a paper shear for shearing continuous forms or bursting the forms along their perforations.
In serial printers, continuous forms which have been printed have been traditionally separated from those not printed by manually tearing the paper at a fold or perforation line. Frequently, the forms are separated by tearing the forms against a tear bar or an edge carried by the printer. Certain printers have control features which permit the printed media to be moved automatically to a convenient tear-off position whereby the fold or perforation lines are accessible, for example, for tearing against an edge.
In a known paper or form separating mechanism for serial printers, there is provided a sharp, knife-edged wheel which engages in a groove formed in a platen. The wheel is drawn across the paper to cut through the form. However, several problems occur with paper separation devices of this type. For example, most forms are quite abrasive and the knife edge is quickly dulled. More importantly, there is a substantial safety hazard when using a knife edge disposed in the printer for separating the forms. For example, the knife must be handled by the operator for installation purposes, i.e., original equipment as well as retrofits, and the sharpness of the knife edge constitutes a safety hazard. Additionally, the knife is often located near the ribbon adjacent the print line of the carriage. Thus, when an operator changes the print ribbon, his hand or hands must be located and manipulated in the immediate vicinity of the sharpened knife edge, rendering the operator vulnerable to injury. This problem has been recognized and protective safety covers have been proposed for installation about the sharp edges of the knife to reduce these safety hazards. However, the knife blade, at least in operation, must, by necessity, protrude past the safety cover to sever the form. Because of the danger of inadvertent contact by an individual with the knife edge, most serial printers do not contain apparatus for automatically severing the printed portion of continuous forms from the unprinted form portion.
Concurrently, however, recent developments in the sophistication of serial printer paper handling have made the ability to cut forms or burst perforations much more important. For example, remote operation of a printer with two or more parkable continuous form paper paths is highly desirable. That type of operation requires an apparatus for automatically separating the continuous forms.
More particularly, it is desirable to print on one type of a continuous form, remove that printed form from the unprinted continuous form and then print on another type of continuous form and remove that printed form from the second continuous form and so on. The capacity to print on different continuous forms using one printer is thus a highly desirable print feature necessitating use of a form separating mechanism.
According to the present invention, there is provided a paper shear for use on serial printers for shearing continuous forms or bursting their perforations which eliminates or minimizes the foregoing and other disadvantages associated with the above-discussed and other printer paper separation devices and provides a novel and improved paper shear and a method of shearing continuous forms. Particularly, the present invention provides a paper shear which does not rely on a sharpened or knife edge for severing the paper and therefore does not present the above-identified and other safety problems associated with a forms separating device having a knife edge. To accomplish this, the paper shear hereof preferably comprises a cylindrical disk or a slightly conically shaped disk mounted on a mechanism for engaging and disengaging the shear relative to the paper and which mechanism, in turn, is carried by the print head carriage. Carriage motion is employed to displace the shear into a position wherein a paper shearing action, rather than a paper cutting action, is provided.
To accomplish this, the paper shear is mounted for movement between a first position retracted from an associated shear platen and a second position poised for engagement with a resisting edge on the shear platen. When it is desired to shear paper in the printer, the appropriate printer control displaces the carriage into a position adjacent an extreme end of its travel, at which time an actuator displaces the paper shear from the first position into an intermediate position spaced from a recessed edge of the shear platen and to one side of the paper in the printer. The shear platen is thus poised beyond the lateral edge of the paper in the printer for traversing movement across the paper with the carriage. To provide a shearing action, the shear platen has a cam edge spaced longitudinally from the recessed edge of the platen. Thus, at the beginning of carriage movement in the direction crossing the paper, the carriage displaces the shear from the recessed platen edge and along the cam edge thereof, eliminating the clearance therebetween and creating an interference between a resisting edge of the shear platen and the shear. With the form to be cut lying against the shear platen, further traversing movement of the carriage draws the paper shear into engagement with and across the paper, shearing the form. The printed form can then be ejected from the printer and the unprinted paper parked in its paper path or returned to the print line. Upon reaching the end of carriage movement in that one traversing direction, the paper shear is displaced into its disengaged position relative to the forms.
In accordance with another aspect of the present invention, there is provided a modular linkage mechanism for displacing the paper shear between positions engaging and disengaging the paper shear and the resisting edge of the shear platen by converting a translational motion of the carriage to a rotational motion of the paper shear. The paper shear and mechanism also provide stops and locking angles for guaranteed engagement and disengagement. For example, paper shear engagement and disengagement positions relative to the shear platen are maintained by an overcenter spring which holds the paper shear in its desired position. Moreover, the paper shear is further maintained in its engaged position by a bias applied thereto when the paper shear is engaged and the carriage is moved in the direction shearing the form. Carriage motion in the opposite direction tends to disengage the paper shear from the shear platen.
The present invention is particularly useful with printers which enable two different forms to be sequentially printed. In printers of that type, there are a pair of parkable continuous forms paper paths enabling the printer to be loaded with two different forms simultaneously. Bills and receipts at a retail outlet or tickets and itinerary at a travel agency are examples of these two different types of forms. The paper shear hereof enables each form to be printed and then sheared off. The other form can then be printed and sheared. Thus, bills and receipts can be intermingled and sheared on the same printer for collation without operator intervention. Likewise, ticket stock and itinerary can be mixed and sheared on the same printer for removal and collation such that a first string of tickets goes with the first itinerary right behind them. Manual intervention is thus not required.
In a preferred embodiment according to the present invention, there is provided a paper printer comprising a paper shear, means carried by the printer mounting the paper shear for movement traversing the paper in the printer, a shear platen carried by the printer, the platen having a surface for bearing engagement with the paper being printed and a resisting edge adjacent the surface and means for selectively engaging and disengaging the paper shear and platen such that, when engaging the platen, the paper shear engages the paper and the resisting edge to shear the paper in response to traversing movement of the paper shear.
In a further preferred embodiment according to the present invention, there is provided a paper printer, comprising a carriage carried by the printer for movement traversing the paper in the printer, a paper shear carried by the carriage for movement therewith traversing the paper in the printer, a shear platen fixed in the printer and means for selectively engaging and disengaging the paper shear and the platen such that, when engaging the platen, the paper shear engages the paper to shear the paper in response to traversing movement of the paper shear. Means responsive to traversing movement of the carriage are also provided for displacing the paper shear between one of the engaged and disengaged positions and the other of the engaged and disengaged positions.
In accordance with another aspect of the present invention, there is provided, in a paper printer carrying a paper shear and a shear platen, a method of shearing the paper comprising the steps of, displacing the paper shear from a first position spaced from the shear platen into a second position adjacent an edge of the shear platen, traversing the paper shear across the width of the paper in the printer when the paper shear lies in the second position and, when in the second position, engaging the paper shear with the platen such that the paper shear engages the paper and the edge to shear the paper in response to traversing movement of the paper shear.
Accordingly, it is a primary object of the present invention to provide a novel and improved paper shear for serial printers which employs a shearing rather than cutting action to separate the forms, thereby eliminating safety hazards associated with sharp edges and to provide a novel and improved linkage for engaging and disengaging the paper shear and a shear platen, as well as to lock the shear platen in predetermined positions.
It is also an object of this invention to provide a novel and improved method of shearing continuous forms in serial printers.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.